Opinion: Allison shows ignorance linked to storm prediction

Jim CarrierSpecial to Newsday

Published Thursday, June 21, 2001

For almost two weeks a tropical storm formally known as Allison wreaked havoc on the United States, causing evacuations, power failures, serious flooding and deaths. And its winds never even reached hurricane force.

In the New York region as much as 5.5 inches of rain fell over the weekend. There were delays at Newark Airport and temporary closings on the Bronx River Parkway and the Saw Mill River Parkway. In a suburb north of Philadelphia four people died in a flooded apartment building that caught fire. Some parts of Pennsylvania got hit with more than 10 inches of rain. But the Gulf States, where 39 people lost their lives, suffered worse.

In the week after Allison sprang to life off Galveston on June 5, the storm dumped 3 feet of rain in parts of Houston, then -- stripped of its tropical designation -- moseyed across the deep South leaving 10 inches of rain in Florida, 7 inches in Georgia, and, filling a 12-inch rain gauge in 14 hours at a South Carolina fire department.

The National Hydrometeorological Prediction Center in Maryland estimates that during that week Allison poured 100 million acre-feet of water on the United States, a year's supply for the entire country. To date, destruction tops $2 billion and counting.

Weather professionals who worked Allison were struck with awe both by the storm's persistent power and their own ignorance about these extreme events. For those stationed along America's eastern coastlines, Allison is also a jangling wake-up call that another hurricane season is upon us. Roughly 10 more storms -- each a rolling crap game of death and destruction -- are coming.

When I began writing this, the storm was dumping its 33 trillionth gallon of water on the South and threatening resurrection as a full-blown tropical depression off North Carolina. Amid the radar blob of red and green convection with its lightning and torrential downpours a telltale counterclockwise curling had resumed. It was not difficult to imagine this beast crawling toward the warm, regenerative energy of the Gulf Stream.

Though a bona fide ''tropical storm'' for only a day, Allison revealed two underappreciated facts about cyclones: the deadly consequences of rain, and the uncertainty of storm forecasts.

After years of measuring hurricanes by wind power -- Category 1 through 5 -- researchers now realize that the real killer is flooding. A new study by Ed Rappaport of the Tropical Prediction Center shows that since 1970 in the United States, 59 percent of deaths were caused by freshwater flooding. Twelve percent were killed by the wind and 11 percent died at sea. Only 1 percent lost their lives in coastal storm surge.

Recent memorable storms bear that out. Hurricane Floyd's heavy rains in 1999 drowned 50 people on the East Coast. Agnes, which struck New York in 1972, killed 122. Overseas, Hurricane Mitch, a 1998 Category 5 storm that smothered Central America and sprang back to life to kill in Florida, did far more damage as a lingering rain event, drowning or burying in mud an estimated 18,000 people.

In heavily paved Houston this month, most people who drowned were in their cars, said Bill Proenza, the National Weather Service's southern regional director. ''We're very macho with our cars,'' he said. ''People think their SUVs can get through a lake, like they are advertised on TV. They underestimate the buoyancy.''

After 50 years of suburbanization around New York, with all its paving and housing, one shudders to think of another ''Long Island Express,'' the 1938 hurricane that flooded New York and Connecticut and killed 600.

As for accuracy, live TV and satellite shots of hurricanes give the impression that forecasters know precisely what's happening. Storm tracks drawn on maps take on a certainty of a road cut through trees.

In fact, the average 24-hour hurricane track forecast is wrong by 100 miles. The average error two days out is 200 miles, a daunting gap for sailors, emergency crews and families trying to decide to flee or stay.

Hurricane Mitch demonstrated that without good data and strong steering currents, computer models can even mislead forecasters into plotting a storm nearly 180 degrees in the wrong direction. Their erroneous forecasts persuaded the captain of a Windjammer Barefoot cruise ship to risk an escape at sea. The ship and 31 men disappeared in the eye wall of the hurricane.

No one is more honest about these errors than the forecasters themselves, who did a pretty good job with Allison's track but again underestimated the inland effects. ''No one expected this much rain,'' said Max Mayfield, the director of the National Hurricane Center.

Local forecasters say their warnings of 10 to 20 inches of rain did alert emergency crews who saved thousands of people. And Doppler radar provided quick readings of where flooding was likely. Still, no one knows precisely where rain will fall until it falls.

When it comes to storms like Allison, the best weather map ever drawn is an obscure government publication showing the combined tracks of more than 900 cyclones since 1886.

From Texas on east, the United States is obliterated under a dark scrawl of lines.

It's plain to see that sometime, everywhere, a hurricane will strike.

Jim Carrier is the author of ''The Ship and the Storm: Hurricane Mitch and the Loss of the Fantome.''